Common-image Gathers Extraction Based On Reverse-time Migration And Amplitude Fidelity Analysis

As the most effective seismic pre-stack depth migration method, reverse-timemigration has many advantages in imaging turning waves or prism waves, handling largelateral velocity variations and in improving amplitude information. And the rapiddevelopment of seismic exploration will inevitably raise a higher requirement on migrationvelocity analysis, amplitude versus offset or amplitude versus angle analysis. In this case, itbecomes more urgent and important to research common-image gathers based on pre-stackreverse-time migration.The first part of the paper compares the one-way wave equation migration methodswith reverse-time migration, summarizes the technique of reverse-time migration, andachieves pre-stack reverse-time migration using high-order finite difference wavefieldcontinuation method. Then the paper introduces the concepts of common-imaging gathers,demonstrates the superiority of angle-domain common-image gathers on handlingmultiarrivals problems and finally realizes the extraction of angle-domain gathers based onone-way wave equation migration. The third part demonstrates that when the geologic dipsare steep, the conventional way of computing common-image gathers does not produce usefulgather since it will cause artifacts. So the paper introduces the concept of verticalangle-domain common-image gathers and the problem can be sidestepped by an appropriatecombination of the two gathers. I demonstrate the need and the advantages of the proposedmethod on model data and real date. Compared with amplitude-preserved one-way waveequation migration methods, the last section analyzes the amplitude information of thecommon-image gathers based on pre-stack reverse-time migration. Then the paper comparesdifferent imaging conditions of reverse-time migration to research amplitude informationfurther. I test these imaging conditions on model date and propose a relativelypreserved-amplitude stable imaging condition.With the development of3D reverse-time migration and elastic reverse-time migration,as well as the extensive application of wide-azimuth seismic acquisition system,3Dangle-domain common-image gathers and isotropic angle-domain common-image gathers will surely continue to grow and mature.